The present invention relates to a process for the preparation of polyalkylphenoxyaminoalkanes. More particularly, this invention relates to a process for the preparation of polyalkylphenoxyaminoalkanes which comprises the aminoethylation of a polyalkylphenol compound with xcex2-amino alcohol and dialkyl carbonate.
Polyalkylphenoxyaminoalkanes are known fuel additives useful in the prevention and control of engine deposits. U.S. Pat. Nos. 5,669,939 and 5,851,242 describe a process for preparing these compounds. The process involves initially hydroxylating a polyalkylphenol with an alkylene carbonate in the presence of a catalytic amount of an alkali metal hydride or hydroxide, or alkali metal salt, to provide a polyalkylphenoxyalkanol which is subsequently reacted with an appropriate amine to provide the desired polyalkylphenoxyaminoalkane.
2-oxazolidinones or derivatives thereof are well described in the art. For example, Martin E. Dyen and Daniel Swern, Chemistry Reviews (1967), pages 197-246 describes 2-oxazolidinones in detail. The use of 2-oxazolidinones or derivatives thereof in the aminoethylation of phenols is well known in the art. This same reference also describes the preparation of both carbamate derivatives and 2-oxazolidinones using various xcex2-amino alcohols and dialkyl carbonates.
U.S. Pat. No. 4,381,401 discloses the reaction of 2-oxazolidinone or N-substituted derivatives thereof with aromatic amine hydrochlorides at elevated temperatures to produce 1,2-ethanediamines. The 1,2-ethandiamines produced are an important class of materials which are useful as intermediates for the production of pharmaceuticals, photographic chemicals and other compositions.
Japanese Patent Publication No. JP 2592732 B2 discloses a method of producing phenoxyethylamines by reacting, under base conditions, low molecular weight phenols and 2-oxazolidinone. Phenoxyethylamines are important raw materials for pharmaceuticals and pesticides.
German Patent Publication DE 19711004 A1 discloses the use of 2-oxazolidinone to prepare phenoxyaminoalkanes from low molecular weight phenols. 2-4-(Phenoxyphenoxy)ethylamine and ethyl 2-(phenoxyphenoxy)ethylcarbamate are sequentially prepared in high yield and selectivity by the aminoethylation of 4-phenoxyphenol with 2-oxazolidinone under inert atomsphere, followed by amidation of 2-4-(phenoxyphenoxy)ethylamine with carbonate derivatives.
U.S. Pat. No. 6,384,280 teaches the use of 2-oxazolidinone or a derivative thereof in aminoethylation transformations involving high molecular weight polyalkylphenols to provide polyalkylphenoxyaminoalkanes of the type disclosed in U.S. Pat. Nos. 5,669,939 and 5,851,242. There has heretofore not been any teaching wherein the combination of xcex2-amino alcohol and dialkyl carbonate or a derivative thereof has been used in aminoethylation transformations involving high molecular weight polyalkylphenols.
The present invention provides a novel process for the preparation of polyalkylphenoxyaminoalkanes which comprises the aminoethylation of a polyalkylphenol compound in the presence of a basic catalyst with a xcex2-amino alcohol or derivative thereof having the following formula:
xe2x80x83R1NHxe2x80x94CHR2xe2x80x94CH2xe2x80x94OH
wherein R1 and R2 are independently hydrogen, lower alkyl having 1 to about 6 carbon atoms, hydroxyalkylene, phenyl, alkaryl or aralkyl;
and a dialkyl carbonate having the following formula:
(R3O)2CO
wherein R3 is lower alkyl having 1 to about 6 carbon atoms and wherein the polyalkyl group of said polyalkylphenol has an average molecular weight in the range of about 600 to 5,000.
Optionally, the aminoethylation reaction may be carried out with an alcohol co-solvent.
The aminoethylation reaction of the present invention readily occurs using a basic catalyst selected from the group consisting of alkali metal lower alkoxides, alkali hydrides or alkali metal hydroxides in the temperature range of about 100xc2x0 C. to 250xc2x0 C., wherein the molar ratio of xcex2-amino alcohol and dialkyl carbonate to polyalkylphenol compound is about 0.9-5:0.9-5:1, wherein the molar ratio of the optional alcohol co-solvent to polyalkylphenol compound, when it is used, is about 0.2:1 to 5:1 and wherein the number of equivalents of basic catalyst per equivalent of polyalkylphenol is about 0.05:1 to 1:1.
Prior to discussing the present invention in detail, the following terms will have the following meanings unless expressly stated to the contrary.
The term xe2x80x9calkylxe2x80x9d refers to both straight- and branched-chain alkyl groups. 
The term xe2x80x9calkarylxe2x80x9d refers to the group:
wherein Ra and Rb are each independently hydrogen or an alkyl group, provided at least one of Ra and Rb is alkyl. Typical alkaryl groups include, for example, tolyl, xylyl, cumenyl, ethylphenyl, butylphenyl, dibutylphenyl, hexylphenyl, octylphenyl, dioctylphenyl, nonylphenyl, decylphenyl, didecylphenyl, dodecylphenyl, hexadecylphenyl, octodecylphenyl, icosphenyl, tricontylphenyl, and the like.
The term xe2x80x9calkylphenylxe2x80x9d refers to an alkaryl group of the above formula in which Ra is alkyl and Rb is hydrogen.
The term xe2x80x9caralkylxe2x80x9d refers to the group: 
Wherein Rc and Rd are each independently hydrogen or a lower alkyl group, and Re is an alkylene group. Typical aralkyl groups include, for example, benzyl, methylbenzyl, ethylbenzyl, propylbenzyl, dimethylbenzyl, phenethyl, and the like.
The term xe2x80x9chydroxyalkylenexe2x80x9d refers to the group:
HOxe2x80x94Rf
wherein Rf is a lower alkylene group as defined below.
The term xe2x80x9clower alkylxe2x80x9d refers to alkyl groups having 1 to about 6 carbon atoms and includes primary, secondary and tertiary alkyl groups. Typical lower alkyl groups include, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl, n-pentyl, n-hexyl, cycloalkyl such as cyclopentyl, cyclohexyl and the like.
The term xe2x80x9clower alkylenexe2x80x9d refers to an alkylene group having 1 to about 6 carbon atoms, such as methylene, ethylene, propylene, butylene, pentylene, and hexylene.
The term xe2x80x9cpolyalkylxe2x80x9d refers to an alkyl group which is generally derived from polyolefins which are polymers or copolymers of mono-olefins, particularly 1-mono-olefins, such as ethylene, propylene, butylene, and the like. Preferably, the mono-olefin employed will have about 2 to 24 carbon atoms, and more preferably, about 3 to 12 carbon atoms. More preferred mono-olefins include propylene, butylene, particularly isobutylene, 1-octene and 1-decene. Polyolefins prepared from such mono-olefins include polypropylene, polybutene, especially polyisobutene, and the polyalphaolefins produced from 1-octene and 1-decene.
As noted above, the present invention provides a novel process for the preparation of polyalkylphenoxyaminoalkanes which comprises an aminoethylation of a polyalkylphenol compound in the presence of a basic catalyst with xcex2-amino alcohol or derivative thereof having the following structure:
R1NHxe2x80x94CHR2xe2x80x94CH2xe2x80x94OH
wherein R1 and R2 are independently hydrogen, lower alkyl having 1 to about 6 carbon atoms, hydroxylalkylene, phenyl, alkaryl, or aralkyl;
and a dialkyl carbonate having the following formula:
xe2x80x83(R3O)2CO
wherein R3 is lower alkyl having 1 to about 6 carbon atoms; and wherein the polyalkyl group of said polyalkylphenol has an average molecular weight in the range of about 600 to 5,000.
Optionally, the aminoethylation reaction may be carried out with an alcohol co-solvent. The optional alcohol co-solvent has the structure R4xe2x80x94OH wherein R4 is an alkyl group having about 4 to 13 carbon atoms.
The reaction may be illustrated by the following: 
wherein R is a polyalkyl group having a molecular weight in the range of about 600 to 5,000, and R1, R2 and R3 are as herein described.
Polyalkylphenoxyaminoalkanes may be prepared by the process of the present invention which comprises an aminoethylation of a polyalkylphenol compound with xcex2-amino alcohol or derivative thereof having the following formula:
R1NHxe2x80x94CHR2xe2x80x94CH2xe2x80x94OH
and a dialkyl carbonate having the following formula:
(R3O)2CO
wherein R1, R2 and R3 are defined herein, in the presence of a catalytic amount of an alkali metal lower alkoxide, alkali hydride or alkali metal hydroxide and, optionally, in the presence of an alcohol co-solvent.
Polyalkylphenols are well known materials and are typically prepared by the alkylation of phenol with the desired polyolefin or chlorinated polyolefin. A further discussion of polyalkylphenols can be found, for example, in U.S. Pat. Nos. 4,744,921 and 5,300,701.
Accordingly, polyalkylphenols may be prepared from the corresponding olefins by conventional procedures. For example, polyalkylphenols may be prepared by reacting the appropriate olefin or olefin mixture with phenol in the presence of an alkylating catalyst at a temperature of from about 25xc2x0 C. to 150xc2x0 C., and preferably about 30xc2x0 C. to 100xc2x0 C. either neat or in an essentially inert solvent at atmospheric pressure. A preferred alkylating catalyst is boron trifluoride. Molar ratios of reactants may be used. Alternatively, molar excesses of phenol can be employed, i.e., about 2 to 3 equivalents of phenol for each equivalent of olefin with unreacted phenol recycled. The latter process maximizes monoalkylphenol. Examples of inert solvents include heptane, benzene, toluene, chlorobenzene and 250 thinner which is a mixture of aromatics, paraffins and naphthenes. Other examples of inert solvents that are aromatic mixtures include Exxon Aromatic 100, Exxon Aromatic 150, Solvesso 100, Total Solvarex 9 and the like.
The polyalkyl group on the polyalkylphenols employed in the invention is generally derived from polyolefins which are polymers or copolymers of mono-olefins, particularly 1-mono-olefins, such as ethylene, propylene, butylene, and the like. Preferably, the mono-olefin employed will have about 2 to 24 carbon atoms, and more preferably, about 3 to 12 carbon atoms. More preferred mono-olefins include propylene, butylene, particularly isobutylene, 1-octene and 1-decene. Polyolefins prepared from such monoolefins include polypropylene, polybutene, especially polyisobutene, and the polyalphaolefins produced from 1-octene and 1-decene.
The preferred polyisobutenes used to prepare the presently employed polyalkylphenols are polyisobutenes which comprise at least about 20% of the more reactive methylvinylidene isomer, preferably at least about 50% and more preferably at least about 70%. Suitable polyisobutenes include those prepared using BF3 catalysts. The preparation of such polyisobutenes in which the methylvinylidene isomer comprises a high percentage of the total composition is described in U.S. Pat. Nos. 4,152,499 and 4,605,808. Such polyisobutenes, known as xe2x80x9creactivexe2x80x9d polyisobutenes, yield high molecular weight alcohols in which the hydroxyl group is at or near the end of the hydrocarbon chain. Examples of suitable polyisobutenes having a high alkylvinylidene content include Ultravis 30, a polyisobutene having a number average molecular weight of about 1,300 and a methylvinylidene content of about 74%, and Ultravis 10, a polyisobutene having a number average molecular weight of about 950 and a methylvinylidene content of about 76%, both available from British Petroleum.
Typically, the polyalkyl group on the polyalkylphenol has a molecular weight in the range of about 600 to 5,000, preferably about 600 to 3,000, more preferably about 700 to 3,000, and most preferably about 900 to 2,500. The polyalkyl group on the polyalkylphenol may be in any position in the phenol ring. However, substitution at the para position is preferred.
As noted above, the polyalkylphenol compound is reacted with xcex2-amino alcohol or a derivative thereof and dialkyl carbonate having the formulas illustrated herein above, wherein R1 and R2 are independently hydrogen or lower alkyl having 1 to about 6 carbon atoms, hydroxyalkylene, phenyl, alkaryl or aralkyl; and R3 is lower alkyl having 1 to about 6 carbon atoms. Typically, the hydroxyalkylene group will have 1 to about 6 carbon atoms, preferably 1 to about 4 carbon atoms. Preferably, R1 and R2 are independently hydrogen or lower alkyl. More preferably, one of R1 and R2 is hydrogen or lower alkyl of 1 to about 4 carbon atoms and the other is hydrogen; and R3 is lower alkyl having 1 to about 4 carbon atoms. In a further preferred embodiment, one of R1 and R2 is hydrogen, methyl, ethyl, hydroxymethylene or hydroxyethylene, and the other is hydrogen, while R3 is methyl, ethyl, propyl, isopropyl, butyl, or isobutyl. More preferably, R1 is hydrogen, methyl or ethyl, R2 is hydrogen or hydroxyethylene, and R3 is methyl, ethyl, propyl, isopropyl, butyl, or isobutyl. Still more preferably, both R1 and R2 are hydrogen and R3 is methyl or ethyl. Most preferably, both R1 and R2 are hydrogen and R3 is ethyl.
Martin E. Dyen and Daniel Swern, Chemistry Reviews (1967), Table II, pages 201-202 describe many examples of xcex2-amino alcohols that react with dialkyl carbonates to form carbamate intermediates and 2-oxazolidinones. In the present invention, both the carbamate intermediate and the 2-oxazolidinone are generated in situ from the xcex2-amino alcohol and the dialkyl carbonate, and then each can independently form polyalkylphenoxyaminoalkanes by aminoethylation of a polyalkylphenol.
More specific examples xcex2-amino alcohols include ethanolamine, diethanolamine, 2-(methylamino)-ethanol, 2-(ethylamino)-ethanol, 2-(n-propylamino)-ethanol, 2-(n-butylamino)-ethanol, 2-amino-1-propanol, 2-amino-1-butanol, 2-amino-1,3-propanediol, xcex2-amino-benzeneethanol, 2-(phenylamino)-ethanol, and 2-(cyclohexylamino)-ethanol. Preferred are ethanolamine, diethanolamine, 2-(methylamino)-ethanol or 2-amino-1-propanol. Most preferably, the xcex2-amino alcohol is ethanolamine.
Examples of dialkyl carbonates are dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate and diisobutylcarbonate. Preferred are dimethyl carbonate or diethyl carbonate. Most preferably, the dialkyl carbonate is diethyl carbonate.
Many of the xcex2-amino alcohols and dialkyl carbonates of the present invention may be purchased from Aldrich Chemical Company or from other laboratory chemical suppliers. Alternatively, these compounds may be synthesized by conventional methods apparent to the skilled artisan.
The basic catalyst employed in the process of the present invention will generally be any of the well known basic catalyst selected from the group of alkali metal lower alkoxides, alkali hydrides or alkali metal hydroxides. Typical alkali metal lower alkoxides include, but are not limited to, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium propoxide, potassium propoxide, sodium isopropoxide, potassium isopropoxide, sodium butoxide, potassium butoxide. Typically, the alkali metal lower alkoxides will contain 1 to about 6, preferably 1 to about 4, carbon atoms. Preferably, the alkali metal lower alkoxide is sodium methoxide. Sodium hydride and potassium hydride are typical alkali hydrides. Examples of alkali metal hydroxides include, but are not limited to, sodium hydroxide, lithium hydroxide, or potassium hydroxide. Sodium hydroxide and potassium hydroxide are preferred.
Typically, the reaction temperature for the aminoethylation reaction will be in the range of about 100xc2x0 C. to 250xc2x0 C., and preferably in the range of about 130xc2x0 C. to 210xc2x0 C. The reaction pressure will generally be atmospheric or lower. Lower pressures may be used to facilitate the removal of carbon dioxide. Other carbon dioxide scavengers may be employed to facilitate the reaction, such as, for example, magnesium oxide or calcium oxide.
The molar ratio of xcex2-amino alcohol and dialkyl carbonate to the polyalkylphenol compound is normally in the range of about 0.9-5:0.9-5:1, and preferably will be in the range of about 1-2:1-2:1. In general, the number of equivalents of the basic catalyst per equivalents of polyalkylphenol will be in the range of about 0.05:1 to 1:1, and preferably in the range of about 0.1:1 to 1:1.
The aminoethylation reaction may be carried out neat or in the presence of a solvent which is inert to the reaction of the polyalkylphenol compound and the xcex2-amino alcohol and dialkyl carbonate or a derivative thereof. When employed, a typical solvent is an aromatic solvent such as Exxon 150 aromatic solvent, although other solvents apparent to those skilled in the art may also be used. For example, any number of ethers, aprotic polar solvents or alcohols may also be useful in the process of the present invention.
The presence of an optional alcohol co-solvent is often beneficial to the aminoethylation process. The alcohol co-solvent has the structure R4xe2x80x94OH wherein R4 is an alkyl group having about 4 to 13 carbon atoms, preferably about 6 to 8 carbon atoms, most preferably about 6 carbon atoms. Examples of typical alcohols include n-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, 2-ethyhexanol, and mixed isomers of each of the foregoing alcohols including branched- or straight-chain alcohols. 1-Hexanol is preferred. Examples of commercial alcohols available from ExxonMobil Chemical that are a mix of several isomers include Exxal 6 (hexyl alcohol), Exxal 7 (isoheptyl alcohol), Exxal 10 (decyl alcohol), and Exxal 13 (tridecyl alcohol).
When an alcohol co-solvent is used, the molar ratio of the alcohol co-solvent to the polyalkylphenol compound is normally in the range of about 0.2:1 to 5:1, preferably about 0.4:1 to 2:1, and most preferably about 0.5:1 to 1.5:1.
The aminoethylation reaction will generally be carried out over a period of about 2 to 24 hours, and preferably over a period of about 3 to 20 hours. Upon completion of the reaction, the desired polyalkyphenoxyaminoalkane is isolated using conventional techniques.